Xenograft tissue control for histology

Abstract

An embodiment of the invention is a method of using a xenograft as a control tissue for histology, comprising staining both a patient and a xenograft-derived control sample under substantially similar staining conditions, and assessing the staining outcomes of the two to determine whether the stain was effective for the patient sample. A xenograft has never been used before in histology as a control, as far as the inventors know. The result of using a xenograft as a control is surprisingly advantageous. First, the cell lines grow and differentiate similarly to a human, taking on the general morphology of a real tissue sample. Second, because the same transformed cell line can be grown limitless times in SCID mice, the xenograft control is highly reproducible, leading to a consistent artificial control that is highly manufacturable and subject to genetic manipulation so that antigens or genetic elements may be embedded in the tissue. Another embodiment of the invention is directed generally to a method of making a tissue control substrate, comprising growing a xenograft from a mammalian transformed cell line in a host animal, removing the xenograft from the host animal, processing the xenograft thereby embedding the xenograft tissue in an embedding medium, and finally affixing the embedded xenograft sample onto a substrate. The substrate is generally a microscope slide. The xenograft control slide can then be stained side-by-side with a specimen sample in an automated slide stainer, and act as a control against which the staining quality can be compared. The xenograft control can also be used as a manual staining control. Determining whether the staining was effective for the patient specimen comprises judging the staining intensity of the xenograft control sample to determine if the expected degree and type of staining were realized in the control. If the expected type (nuclear, membranous, or cytoplasmic) and degree (0-4 scale) of staining are realized during the run, then the xenograft control indicates the staining process and reagents are working properly, and so the result in the patient specimen can be trusted. A further embodiment of the invention is a xenograft-derived control slide for histochemical use, comprising at least one xenograft control sample prepared for histological use, and a sample slide upon which the at least one xenograft control sample is affixed.

Description

CROSS-REFERENCE TO RELATED CASES [0001] This application claims priority to U.S. Provisional patent application Ser. No. 60 / 676,056 filed Apr. 29, 2005, the entire contents of which are incorporated by reference herein.BACKGROUND [0002] 1. Field of the Invention [0003] The invention is directed generally to the area of Histology, particularly the area of tissue controls for histochemical processing of patient samples. [0004] 2. Description of Related Art [0005] The use of controls in Histology is essential. Controls are used in all three sub-disciplines including Immunohistochemistry (“IHC”), in situ hybridization (“ISH”) and special stains (“SS”). Traditionally, two types of controls are used, positive and negative. Tissue controls are usually created from either the patient tissue block that is to be run, or from a known, well-characterized archival tissue block. [0006] In IHC, positive control testing is performed on sections of tissue known to contain the target antigen, process...

AI Technical Summary

Benefits of technology

[0017] An embodiment of the invention is a method of using a xenograft as a control tissue for histology, comprising staining both a patient and a xenograft-derived control sample under substantially similar staining conditions, and assessing the staining outcomes of the two to determine whether the stain was effective for the patient sample. A xenograft has never been used before in histology as a control, as far as the inventors know. The result of using a xenograft as a control is surprisingly advantageous. First, the cell lines grow and differentiate similarly to a human, taking on the general morphology of a real tissue sample. Second, because the same transformed cell line can be grown limitless times in SCID or other immunodeficient mice, the xenograft control is highly reproducible, leading to a consistent artificial control that is highly manufacturable.

Problems solved by technology

Internal positive controls are acceptable for these antigens, but unless the internal control tissue is very-well characterized, there is always some concern that the internal control may not be reliable.

Exclusive use of normal tissues that have high levels of antigen expression may result in antibody titers (concentrations) of insufficient sensitivity, leading to false-negative results.

Unexpected positive staining of such tissues indicates that the test has lost specificity, perhaps because of improper antibody concentration or excessive antigen retrieval.

Intrinsic properties of the test tissue may also be the cause of “non-specific” staining.

However, in both positive and negative controls, since the tissue used is non-standardized, it is never fully characterized and so there is always some doubt as to the control's usefulness.

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